Such a discussion gives opportunity for falling out (4-5)
I believe the answer is:
open-ended
'out' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I don't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for open-ended that I've seen before include "Having no fixed limit, perhaps a discussion" , "Without fixed limits or restrictions" , "Allowing free debate with no set time to finish." , "With no fixed limit, not circumscribed" , "Having no predetermined limit" .)